Elements of seamless carbon steel pipe annealing

The glossiness of annealed seamless carbon steel pipe determines the quality of the product. There are many influencing factors. Here are five key factors:

1. Annealing temperature.

Whether the required temperature is reached. The heat treatment process of steel generally adopts heat treatment plus tempering heat treatment process, which is what we usually call "annealing", and the temperature range is 1040~1120°C (Japanese standard).

2. Annealing atmosphere.

The annealing atmosphere generally adopts pure hydrogen, and the purity of the atmosphere is above 99.99%. If the other part of the atmosphere is a noble gas, the purity can be lower, but it can't contain too much CO2 and water vapor.

3. The airtightness of the furnace wall.

The seamless steel pipe furnace should be airtight and isolated from the outside gas; if radon gas is used as a protective gas, only one exhaust pipe (for igniting the discharged radon gas) should be opened. The inspection method can be used to smear soap liquid on the gaps of the joints of the annealing furnace to see if there is gas escaping; the area where the gas is very easy to escape is the area where the annealing furnace enters the pipeline and the area where the pipeline exits. Especially the sealing ring in this place is very easy to wear, so it should be checked and replaced frequently.

4. Protective gas working pressure.

In order to better avoid trace leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is radon protective gas, it is generally stipulated above 20kBar.

5. There is water vapor in the furnace.

On the one hand, check whether the furnace wall raw materials are dry. When installing the furnace for the first time, the raw materials of the furnace wall must be air-dried; on the other hand, whether there is too much water on the seamless steel pipe entering the furnace, especially if there are holes on the top of the pipe, do not let water seep in, otherwise it will destroy the atmosphere in the furnace.

Article source: https://article-realm.com/article/Finance/33964-Elements-of-seamless-carbon-steel-pipe-annealing.html